Electric-furnace control.



J. A. SEEDE.

ELECTRIC FURNACE CONTROL Arrucmox HLED MAY a. 1916.

1,242,250. Patented 0% 9,1917.

Inventor:

John A. eede,

His Attorney.

UNITED STATES PATENT or nron.

JOHN A. SEEDE, OF SCHENECTADY, YORK, ASSIGNOR T GENERAL EIYJEGTRIG COMPANY, A CORPORATION OEINEW YORK.

ELECTRIC FURNACE CONTROL.

Specification of letters Iatent.

To all whom it may concern:

Be it known that I, JOHN A. SEEDE, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Electric-Furnace Controls, of which the following is a specification.

Thepresent invention relatesto the operation of electric furnaces, particularly furnaces of the arc type, and one of its objects is to-provide for a convenient and reliable control of reactance in the furnace circuit.

In the operation of electric furnaces it is often necessary or desirable to insert or withdraw reactance at some stage of the operation. To switch a reactance coil into or out of circuit directly is impracticable for various reasons, for example, because of the heavy currents employed, hence the operation of the furnace must be interrupted to carry "on the switching operation.

' In accordance with my invention, I have provided in inductive relation to a reactance coil in the furnace circuit a secondary cir cuit usually consisting of a different number of turns than the reactance coil in the furnace circuit, for example with a greater number of turns when the furnace current is very large. When it is desired to increase the reactance of the furnace circuit, the secondary coils are open-circuited, and when .the reactance of the furnace circuit is to be reduced the secondary coils are short-circuited.

The accompanying drawing is a diagram of connections illustrating my invention. In the drawing an electric furnace of the .arc type has been diagrammatically represented as comprising a container or crucible 1 and arc-supporting electrodes 2, 3 and 4t which may be assumed to consist of carbon to be of the usual form. The electrodes are respectively supplied with current through conductors 5, 6 and 7 the conductors 5 and 7 being connected to the terminals of the secondary of a transformer 8 and the conductor 6 bein connected to an intermediate point. The primary of the transformer is supplied with current through a three-phase alternating current system fed by conductors 9, 10 and 11. In circuit with "the supply conductors 5 and 7 respectively, are rea e c devices 12 and 13, each of which. may

'15 and high voltage secondary windings 16 and 17. The secondary windings are con- Patented Oct. 9, 1217.. Application filed May 8, 1916; Serial No. 96,046. I

nected to local circuits 18 and 19 containing contactors 20 and 21. The contactor switches may be remotely controlled through magnets 22 and 23. The control magnets 22 and 23 are shown as being connected respectively to conductors 24 and 25 to one terminal of a source of current 26, the opposim terminal of which is grounded as indicated at the point G. The opposite terminals of the conductor magnets are also shown as being grounded at G, this diagrammatic representation being used to indicate either a ground or a metallic return wire. The device 13 similarly has primary windings in circuit with the conductor 7 which suppiie's the electrode 4:. The secondary windings 16', 17 of the transformer may be closed on themselves by contactors 20, 21', operated 'by magnets energizedfrom the source 26 by the closure of switches 29, 30.

By closing either or both the switches 2 or 28, one or both of thesecondary coils of the transformer 12 may be short-circuited thereby reducing the reactance in the supply conductor 5. In the same manner the closure of eachor both switches 29 or 30 will close contactors 20, 21 and thus short-circuit one or both of the secondary coils 16,

17 in the transformer 13, thereby decreasing the reactance in the supply conductor 7. If the secondary windings be made of a relatively large number of turns as compared with the primary windings, the current in the circuit in which the switching is carried out may be correspondingly smaller than the current in the primary or furnace supply circuit. Although the voltage in the secondary circuit is correspondingly higher this need cause no inconvenience as the supply voltage of an arc furnace usually is relatively low, for example about 100 volts, while the current value may be many thousand amperes.

' By thus carrying out the switching operations smaller currents, in accordance with my 111- vention, it is possible to considerably decrease the cost of installation and maintenance and to increase the reliability of the furnace outfit, p

in a secondary circuit' carrying While I have described my invention with reference to an arc furnace, it should be understood as being equally applicable to any industrial furnace, or similar device, using either very heav currents at low voltage, or very high vo tages with relatively small currents.

What I claim as new and desire to secure by Letters Patent of the United States, is,-

l. The combination of an electric furnace, a supply circuit therefor, a reactance' coil in said supply circuit, a secondary coil in inductive relation with said coil, and means for controlling the current in said secondary coil to vary the reactance of the furnace supply circuit.

2. The combination of an electric furnace,

. a supply circuit therefor, a reactanoe coil,

circuit connections including said coil in series with said supply circuit, and means external to said coil for controlling the reactance of said coil While maintaining the circuit connections of said coil undisturbed.

.for each of said circuits havin 3. The combination of an electric furnace age primary winding included in the supply circuit and a hi h voltage secondary circuit closed upon itself, contactors in each of said secondary circuits, and remote I control devices for opening tactors.

4. The combination of an electric furnace, a source of alternating current, circuit connections from said source to said furnace, reactance devices having a primary winding connected in circuit with said furnace, and a secondary winding of a eater number of turns than said primary winding, and means for controlling the current in said secondarywinding.

In Witness whereof, I have hereunto set 3 my hand this 6th day of May, 1916.

' JOHN SEEDE.

and closing said con.- 

